For instance, a car navigation system includes a display apparatus of a liquid crystal display disposed in a central portion of an instrument panel close to a driver seat. This display apparatus displays a map surrounding a current position of a subject vehicle or an input window for input or setting, on its screen. This screen includes a touch screen (also called touch panel or touch switch), which allows a user to performs an input, setting, or instruction by touching the touch screen.
This display apparatus with the touch screen is a superior interface which is easy for a user to see and operate, and therefore adapted to various apparatuses. Furthermore, it is proposed that a user is allowed to change a character size in a manipulation button (icon) on the touch screen for enhancing visibility and operability (see Patent Document 1).
While a user (driver) is driving a vehicle, it is not preferable that the user sees the screen or performs complicated touch manipulation on the touch screen. It is because those user's actions during the driving may disperse concentration on the driving. Therefore, a measure to enhance safety during the driving has been proposed which disables switches on the screen, erases characters, or prohibits user's manipulation.
However, if almost all manipulations are prohibited during the driving, even a manipulation that hardly disturbs the safety during the driving is also precluded. Furthermore, even a manipulation from a driver-assistant seat is also caused to become ineffective. This deteriorates user-friendliness in the apparatus. It is preferable that a user is allowed to perform a minimum manipulation on the touch screen while securing the safety during the driving.
Patent Document 1: JP-2004-180275A (US-2004/0130573A1)